The quantum theory of the laser is used to study the statistical properties of laser radiation due to spontaneous emission from atoms. Here we mean fluctuations of the radiation that are a result of the quantized structure of the electromagnetic field and of the active medium.
The many lasers are required for the different process steps of a quantum computer: generating, cooling, capturing, and preparing the atoms or ions and generating the entanglement. In the past, the technology required for one qubit filled a vibration-cushioned optical laboratory bench that weighed a hundred kilograms.
Quantum Technology: Lasers for Communication
Using lasers for quantum information
It was only short time after the formulation and acceptance of quantum theory when scientists started to discuss possible benefits of this theory for mankind. The quantum computer, probably the most famous application of quantum theory, is expected to reach incredible computing speeds that enable calculations which were not possible before. Any coupled quantum mechanical system can be used for quantum computing. Solid state systems, trapped ions, atoms in optical lattices, and photons with linear optical elements are at the heart of quantum computer research. First quantum operations have been demonstrated with solid state systems and trapped ions but the race is still open.
Advanced Laser Technology for Quantum Communications (Tutorial Review)